The invention concerns a method of producing bristles for applying media through extrusion of a filament which can be cut into bristles and provided with cavities for receiving the medium and from which the medium is discharged during proper use of the bristles, as well as a bristle and brushes comprising such bristles produced in accordance with this method.
Brushes comprising bristles for applying liquid, viscous or powdery media are used mainly for body, hair and mouth care but also in the household and for technical applications. The invention is described below mainly in connection with tooth brushes, one of the main fields of application.
Tooth brushes are known which highlight film on the teeth through application of a suitable indicating color to allow the user of the tooth brush to increase brushing of such indicated tooth locations (DE 195 45 644). Towards this end, the brushes are coated with the indicating color or with microcapsules containing the color and the coating is optionally sealed. A hollow brush with inserted indicating medium is also described in this connection. This document does not explain in detail how these hollow brushes are filled. It is further known (CA 549 168) to jacket the brushes of a single-use tooth brush with a tooth care medium. Bristles are also known (U.S. Pat. No. 5,678,275) whose circumference is provided with irregularly shaped grooves. They do not accommodate media but are supposed to accept soilage particles to remove them from the mouth during brushing of the teeth.
It is furthermore known (WO 98/24341) to accommodate therapeutically effective or other media having dental medical effects in a hollow brush which are released at the free open end of the brush during use. The hollow brush is optionally reinforced by radial walls such that it comprises three or four chambers with parallel axes. The desired media are introduced in liquid form. Towards this end, filaments having the cross-sectional shape of the finished bristles are extruded and several filaments are combined into multi-veined strands having a diameter up to 5.5 cm and a length up to 1.2 m. One end of the strand is dipped into the liquid medium and suction is applied to the opposite open ends of the filaments. Since a high suction pressure is required due to the capillary cavities and the large strand length and since collapsing of the walls due to the elasticity of a suitable plastic must be prevented, the wall must be quite thick and complete filling of the hollow bristles is not possible. Viscous or dispersed media cannot be introduced into the capillary cavities due to the high pressure drop. During use of the bristle, the medium is only discharged via the open end of the bristles and is therefore fully undefined and incomplete.
U.S. Pat. No. 4,775,585 describes a polymer article e.g. in the form of a fiber having a solid cross section. A medium is introduced into portions of the cross section which should be dispensed when the fiber is in use. The portions of the fiber containing the medium can be circular sectors distributed about the periphery or could form an outer ring of the cross section. This configuration does not lead to defined release of the medium.
U.S. Pat. No. 4,010,308 discloses a fiber having a porous coating, hollow portions of which accommodate a medium. The hollow cavities result in relatively rapid and undefined release of the medium. An electrically conducting fiber can be created by using of an electrolyte as the medium and the outer surface of the fiber can be provided with an insulating, impermeable shellac coating. No medium release is therefore envisioned.
It is the underlying purpose of the invention to propose a method for economical introduction of media of arbitrary consistency and effect into a bristle and for discharge thereof in a desired dosage during the useful life of the bristle.